linux-kernel - Re: [PATCH 1/5] sched/fair: ignore SIS

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Date:   Mon, 15 Aug 2022 10:44:17 +0800
From:   Abel Wu <wuyun.abel@...edance.com>
To:     Chen Yu <yu.chen.surf@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Josh Don <joshdon@...gle.com>, Chen Yu <yu.c.chen@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] sched/fair: ignore SIS_UTIL when has idle core

Hi Chen, thanks for your testing!

On 8/10/22 9:50 PM, Chen Yu Wrote:
> On Tue, Jul 12, 2022 at 4:45 PM Abel Wu <wuyun.abel@...edance.com> wrote:
>>
>> When SIS_UTIL is enabled, SIS domain scan will be skipped if
>> the LLC is overloaded. Since the overloaded status is checked
>> in the load balancing at LLC level, the interval is llc_size
>> miliseconds. The duration might be long enough to affect the
>> overall system throughput if idle cores are out of reach in
>> SIS domain scan.
>>
>> Signed-off-by: Abel Wu <wuyun.abel@...edance.com>
>> ---
>>
> Tested schbench and netperf on latest 5.19 vanilla, it seems that there
> is latency performance improvement when the load is low in schbench,
> and no performance difference on netperf.
> 
>   ./report.py -b 5.19.0+ -c 5.19.0-skip-sis-util+ -t schbench
> 
> schbench
> ========
> case            load    baseline(std%) compare%( std%)
> normal          mthread-1 1.00 (  0.00) +7.69 (  0.00)
> normal          mthread-2 1.00 (  0.00) +13.24 (  0.00)
> normal          mthread-4 1.00 (  0.00) -5.88 (  0.00)
> normal          mthread-8 1.00 (  0.00) -0.25 (  0.00)
> 
> 
> ./report.py -b 5.19.0+ -c 5.19.0-skip-sis-util+ -t netperf
> netperf
> =======
> case            load    baseline(std%) compare%( std%)
> TCP_RR          thread-28 1.00 (  0.62) +0.15 (  0.55)
> TCP_RR          thread-56 1.00 (  0.42) -0.26 (  0.40)
> TCP_RR          thread-84 1.00 (  0.29) +0.39 (  0.29)
> TCP_RR          thread-112 1.00 (  0.22) +0.44 (  0.23)
> TCP_RR          thread-140 1.00 (  0.17) +0.33 (  0.18)
> TCP_RR          thread-168 1.00 (  0.17) +0.19 (  0.16)
> TCP_RR          thread-196 1.00 ( 13.65) -0.62 ( 14.83)
> TCP_RR          thread-224 1.00 (  9.80) -0.65 (  9.67)
> UDP_RR          thread-28 1.00 (  0.89) +0.92 (  0.81)
> UDP_RR          thread-56 1.00 (  0.78) +0.38 (  0.73)
> UDP_RR          thread-84 1.00 ( 14.03) +0.78 ( 16.85)
> UDP_RR          thread-112 1.00 ( 12.26) -0.42 ( 11.95)
> UDP_RR          thread-140 1.00 (  9.86) -0.89 (  6.93)
> UDP_RR          thread-168 1.00 ( 11.62) -0.82 (  8.80)
> UDP_RR          thread-196 1.00 ( 19.47) +0.42 ( 16.50)
> UDP_RR          thread-224 1.00 ( 18.68) +0.72 ( 18.50)
> 
> 
> Tested-by: Chen Yu <yu.c.chen@...el.com>
>